Sheet ejection device and image forming apparatus incorporating the sheet ejection device

ABSTRACT

A sheet ejection device includes a sheet stacker, a retainer, and a biasing member. The sheet stacker has a stacker face and a coupling portion. The sheet stacker is configured to stack a sheet on the stacker face. The retainer has a coupling portion and an adjuster configured to rotate the sheet stacker to adjust an angle of the stacker face. The retainer is configured to retain the sheet stacker to be movable in a vertical direction. The biasing member is coupled to the sheet stacker and the retainer to apply a biasing force to bias the sheet stacker in an upward direction to the retainer. The sheet stacker is configured to move in a downward direction against the biasing force, as a number of sheets stacked on the stacker face increases. The coupling portion of the retainer is configured to move when the adjuster rotates the sheet stacker.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-033696, filed on Feb. 27, 2019, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND Technical Field

This disclosure relates to a sheet ejection device to eject a sheet such as paper, and an image forming apparatus incorporating the sheet ejection device. The image forming apparatus corresponds, for example, to a copier, printer, facsimile machine, printing machine, and a multi-functional apparatus including at least two functions of the copier, printer, facsimile machine, and printing machine.

Discussion of the Background Art

Various types of image forming apparatuses such as copiers, printers, and printing machines are known to include a sheet ejection device provided with a sheet stacker (in other words, a sheet tray) that stacks sheets such as papers ejected from the housing of an image forming apparatus.

There are various types of sheet stackers. Some sheet stackers (i.e., sheet trays) are rotatable to appropriately change an angle of a stacker face on which a sheet is stacked while some sheet stackers (i.e., sheet trays) are vertically movable to move in a vertical direction, according to the number of sheets to be stacked on the sheet stacker.

SUMMARY

At least one aspect of this disclosure provides a sheet ejection device including a sheet stacker, a retainer, and a biasing member. The sheet stacker has a stacker face and a coupling portion. The sheet stacker is configured to stack a sheet on the stacker face. The retainer has a coupling portion and an adjuster configured to rotate the sheet stacker to adjust an angle of the stacker face. The retainer is configured to retain the sheet stacker to be movable in a vertical direction. The biasing member is coupled to the sheet stacker and the retainer and configured to apply a biasing force to bias the sheet stacker in an upward direction to the retainer. The sheet stacker is configured to move in a downward direction against the biasing force of the biasing member, as a number of sheets stacked on the stacker face of the sheet stacker increases. The coupling portion of the retainer, to which the biasing member is coupled, is configured to move when the adjuster of the retainer rotates the sheet stacker.

Further, at least one aspect of this disclosure provides an image forming apparatus including an image forming the above-described sheet ejection device. The image forming device has a sheet ejection unit configured to eject a sheet. The sheet ejection device is configured to stack the sheet ejected by the sheet ejection unit of the image forming device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

An exemplary embodiment of this disclosure will be described in detail based on the following figured, wherein:

FIG. 1 is a schematic view illustrating an overall configuration of an image forming apparatus according to an embodiment of this disclosure;

FIGS. 2A, 2B, and 2C are schematic side views illustrating operations of a sheet ejection device provided in the image forming apparatus of FIG. 1;

FIGS. 3A, 3B, and 3C are schematic top views illustrating operations of a retainer of the sheet ejection device;

FIGS. 4A and 4B are schematic side views illustrating operations of a comparative sheet ejection device according to a comparative example;

FIG. 5A is a schematic diagram illustrating a sheet ejection device according to Variation of the embodiment of this disclosure; and

FIG. 5B is a schematic diagram illustrating a comparative sheet ejection device according to a comparative configuration of FIG. 5A.

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.

DETAILED DESCRIPTION

It will be understood that if an element or layer is referred to as being “on”, “against”, “connected to” or “coupled to” another element or layer, then it can be directly on, against, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, if an element is referred to as being “directly on”, “directly connected to” or “directly coupled to” another element or layer, then there are no intervening elements or layers present. Like numbers referred to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements describes as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors herein interpreted accordingly.

Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layer and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.

The terminology used herein is for describing particular embodiments and examples and is not intended to be limiting of exemplary embodiments of this disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Descriptions are given, with reference to the accompanying drawings, of examples, exemplary embodiments, modification of exemplary embodiments, etc., of a sheet ejection device and an image forming apparatus according to exemplary embodiments of this disclosure. Elements having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted. Elements that do not demand descriptions may be omitted from the drawings as a matter of convenience. Reference numerals of elements extracted from the patent publications are in parentheses so as to be distinguished from those of exemplary embodiments of this disclosure.

This disclosure is applicable to any sheet ejection device and image forming apparatus and is implemented in the most effective manner in an electrophotographic image forming apparatus.

In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes any and all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. In the drawings for explaining the following embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below.

Hereinafter, an electrophotographic image forming apparatus (hereinafter simply referred to as an image forming apparatus) which forms an image by an electrophotographic system is described as an image forming apparatus including a sheet ejection device according to this disclosure. In the following embodiments, a color laser printer is described as an example of the image forming apparatus. However, the image forming apparatus is not limited to a color printer but may be a monochrome printer. The image forming apparatus is not limited to the printer and may be another image forming apparatus such as a copier and a multifunction peripheral. The image forming apparatus including the sheet ejection device according to the present embodiment is not limited to the image forming apparatus of the electrophotographic system and may be an image forming apparatus of another system such as an ink jet system.

Next, a description is given of a configuration and functions of an image forming apparatus according to an embodiment of this disclosure, with reference to drawings. It is to be noted that identical or corresponding parts are given identical reference numerals and redundant descriptions are summarized or omitted accordingly.

Initially, a description is given of an overall configuration and operations of an image forming apparatus 1 according to an embodiment of the present disclosure, with reference to FIG. 1. FIG. 1 is a schematic view illustrating the image forming apparatus 1. The image forming apparatus 1 may be, e.g., a copier, a facsimile machine, a printer, or a multifunction peripheral (MFP) having at least two of copying, printing, scanning, facsimile, and plotter functions.

It is to be noted in the following examples that: the term “image forming apparatus” indicates an apparatus in which an image is formed on a recording medium such as paper, OHP (overhead projector) transparencies, OHP film sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, and/or ceramic by attracting developer or ink thereto; the term “image formation” indicates an action for providing (i.e., printing) not only an image having meanings such as texts and figures on a recording medium but also an image having no meaning such as patterns on a recording medium; and the term “sheet” is not limited to indicate a paper material but also includes the above-described plastic material (e.g., an OHP sheet), a fabric sheet and so forth, and is used to which the developer or ink is attracted. In addition, the “sheet” is not limited to a flexible sheet but is applicable to a rigid plate-shaped sheet and a relatively thick sheet.

Further, size (dimension), material, shape, and relative positions used to describe each of the components and units are examples, and the scope of this disclosure is not limited thereto unless otherwise specified.

Further, it is to be noted in the following examples that: the term “sheet conveying direction” indicates a direction in which a recording medium travels from an upstream side of a sheet conveying path to a downstream side thereof; the term “width direction” indicates a direction basically perpendicular to the sheet conveying direction.

In FIG. 1, the image forming apparatus 1 is a copier in the present embodiment and includes a document reading device 2, an exposure device 3, an image forming device 4, a photoconductor drum 5, a transfer roller 7, a transfer conveyance belt 8, a document conveying unit 10, an upper sheet feed tray 12, a lower sheet feed tray 13, a pair of registration rollers 17, a fixing device 20, a fixing roller 21, a pressure roller 22, a pair of sheet ejection rollers 25, a sheet ejection device 30, and a control display panel 100. The document reading device 2 optically reads image data of an original document D. The exposure device 3 emits an exposure light L based on the image data read by the document reading device 2 to irradiate the exposure light L onto a surface of the photoconductor drum 5 that functions as an image bearer.

The image forming device 4 forms a toner image on the surface of the photoconductor drum 5. The transfer roller 7 contacts the photoconductor drum 5 via the transfer conveyance belt 8 to form a transfer nip region. The transfer conveyance belt 8 functions as a transfer unit to transfer the toner image formed on the photoconductor drum 5, onto a sheet P and conveys the sheet P with the toner image. The document conveying unit 10 (the automatic document transfer device) conveys the original document D set on a document tray to the document reading device 2.

The upper sheet feed tray 12 and the lower sheet feed tray 13 are sheet trays, each of which contains the sheet P (a recording medium P) such as paper. The pair of registration rollers 17 (in other words, a pair of timing rollers) conveys the sheet P toward a transfer nip region.

The fixing device 20 includes the fixing roller 21 and the pressure roller 22 to fix a toner image (specifically, an unfixed image) formed on the sheet P to the sheet P by application of heat by the fixing roller 21 and pressure by the pressure roller 22.

The pair of sheet ejection rollers 25 functions as a sheet ejection device to convey and eject the sheet P from a housing 1A of the image forming apparatus 1. The sheet ejection device 30 stacks the sheet P ejected from the housing 1A of the image forming apparatus 1. The control display panel 100 displays various information functioning on the image forming apparatus 1 and operation buttons (keys) for operating the image forming apparatus 1.

Now, a description is given of regular image forming operations performed by the image forming apparatus 1, with reference to FIG. 1.

First, the original document D is conveyed (fed) from a document loading table provided to the document conveying unit 10 and conveyed by multiple pairs of sheet conveying rollers disposed in the document conveying unit 10 in a direction indicated by arrow in FIG. 1, passing over the document reading device 2. At this time, the document reading device 2 optically reads image data of the original document D passing over the document reading device 2.

Consequently, the image data optically scanned by the document reading device 2 is converted to electrical signals. The converted electrical signals are transmitted to the exposure device 3 (in other words, a writing portion) by which the image is optically written. Then, the exposure device 3 emits exposure light L (for example, laser light) based on the image data of the electrical signals, toward the surface of the photoconductor drum 5 of the image forming device 4.

By contrast, the photoconductor drum 5 of the image forming device 4 rotates in a clockwise direction in FIG. 1. After a series of predetermined image forming processes (e.g., a charging process, an exposing process, and a developing process) is completed, an image (for example, a toner image) corresponding to the image data is formed on the surface of the photoconductor drum 5.

Then, the toner image formed on the surface of the photoconductor drum 5 is transferred onto the sheet P that is conveyed by the pair of registration rollers 17, in the transfer nip region (i.e., a position at which the transfer roller 7 contacts the photoconductor drum 5 via the transfer conveyance belt 8).

Now, a description is given of how to operate the sheet P conveyed to the transfer nip region.

First, as illustrated in FIG. 1, one sheet feed tray of the upper sheet feed tray 12 and the lower sheet feed tray 13 of the housing 1A of the image forming apparatus 1 is selected automatically or manually. In the operations according to the present embodiment of this disclosure, the upper sheet feed tray 12 that is an uppermost sheet tray is selected, for example. It is to be noted that the upper sheet feed tray 12 and the lower sheet feed tray 13 basically have an identical configuration to each other. Consequently, when the upper sheet feed tray 12 of the image forming apparatus 1 is selected, an uppermost sheet P contained in the upper sheet feed tray 12 is fed by a sheet feeding mechanism 52 toward a sheet conveyance passage. The sheet feeding mechanism 52 includes a sheet feed roller, a pickup roller, a backup roller, and so forth. The uppermost sheet P passes through the sheet conveyance passage, in which multiple sheet conveying rollers are disposed, and then reaches the pair of registration rollers 17.

After reaching the pair of registration rollers 17, the sheet P is conveyed toward the transfer nip region in synchronization with movement of the toner image formed on the surface of the photoconductor drum 5 for positioning.

After completion of this transfer process, the sheet P passes the position of the transfer nip region, is conveyed by the transfer conveyance belt 8, and then reaches the fixing device 20. In the fixing device 20, the sheet P is conveyed between the fixing roller 21 and the pressure roller 22, so that the toner image is fixed to the sheet P by application of heat applied by the fixing roller 21 and pressure applied by the fixing roller 21 and the pressure roller 22, which is a fixing process. The sheet P with the toner image fixed to the sheet P in the fixing process is conveyed out from the fixing roller 21 and the pressure roller 22 (in other words, a fixing nip region). Then, the sheet P is ejected from the housing 1A of the image forming apparatus 1 by the pair of sheet ejection rollers 25, to be stacked as an output image on the sheet stacker 31 (that is, the sheet ejection tray).

Thus, a series of the image forming processes is completed.

Next, a detail description is given of the sheet ejection device 30 according to the present embodiment.

As described above with reference to FIG. 1, the sheet ejection device 30 is a device on which the sheets P are stacked after the sheets P are conveyed and ejected by the pair of sheet ejection rollers 25.

FIGS. 2A, 2B, and 2C are schematic side views illustrating operations of the sheet ejection device 30. In reference to FIG. 2A, the sheet ejection device 30 according to the present embodiment includes a sheet stacker 31, a retainer 32, and a compression spring 33 that functions as a biasing member.

The pair of sheet ejection rollers 25 is disposed in a sheet ejection portion that is an opening formed in the housing 1A of the image forming apparatus 1. The sheet stacker 31 has a stacker face (that is, a part indicated by a broken line in FIG. 1). The sheet stacker 31 is configured to stack the sheet P ejected from the pair of sheet ejection rollers 25, onto the stacker face.

The retainer 32 is configured to retain the sheet stacker 31 to be movable in a vertical direction of the image forming apparatus 1. The retainer 32 includes a fixed retaining portion 32 a, a rotary retaining portion 32 b, and a movable member 32 c that functions as an adjuster.

The compression spring 33 is coupled to the sheet stacker 31 and the retainer 32. The compression spring 33 functions as a biasing member to bias the sheet stacker 31 in an upward direction, relative to the retainer 32. Specifically, the retainer 32 has a coupling portion 32 d (in other words, a receiving portion) and the sheet stacker 31 has a coupling portion 31 d (in other words, a receiving portion). One end of the compression spring 33 (that is, a biasing member) is coupled to the coupling portion 32 d of the retainer 32 and an opposed end of the compression spring 33 is coupled to the coupling portion 31 d of the sheet stacker 31.

Here, in the present embodiment, the sheet stacker 31 moves in a downward direction against the biasing force of the compression spring 33 that functions as a biasing member, as the number of sheets P stacked on the stacker face increases.

More specifically, as illustrated in FIG. 2A, when no sheet P is stacked on (the stacker face of) the sheet stacker 31, the sheet stacker 31 is lifted and located at an uppermost position due to the biasing force of the compression spring 33. As illustrated in FIG. 2B, as the sheet P is stacked one by one into a sheet bundle, on (the stacker face of) the sheet stacker 31, the sheet stacker 31 gradually lowers against the biasing force of the compression spring 33, due to an increase in the weight of the sheet bundle. At this time, the degree of lowering of the sheet stacker 31 (in other words, the amount of the biasing force of the compression spring 33) is set to keep a height H1 from the pair of sheet ejection rollers 25 (i.e., the sheet ejection portion) to the stacker face (specifically, to the top face of an uppermost sheet in a case in which the sheets P are stacked on the stacker face). That is, in FIG. 2B, the spring force of the compression spring 33, whose length of use M is shrunk from a length of use M1 to a length of use M2, and the weight of the sheets P stacked on the stacker face of the sheet stacker 31 are balanced.

Accordingly, regardless of the number of sheets P stacked on the stacker face, the posture in which the sheet P ejected by the pair of sheet ejection rollers 25 lands on the stacker face (or the top face of the uppermost sheet P on the stacker face) in a stable posture. Therefore, the sheets P are stacked orderly on the sheet stacker 31, in other words, the stacking performance is enhanced.

Further, in the present embodiment, the retainer 32 includes the movable member 32 c that functions as an adjuster to rotate the sheet stacker 31 so as to adjust the angle of the sheet stacker 31 to the housing 1A of the image forming apparatus 1. It is to be noted that the angle of the stacker face of the sheet stacker 31 is an angle of inclination of the sheet P in the sheet conveyance direction (in other words, directions of the leading end to the trailing end of the sheet P). The angle of inclination is formed by the stacker face and a horizontal plane with respect to the sheet stacker 31.

To be more specific, the retainer 32 includes the fixed retaining portion 32 a, the rotary retaining portion 32 b, and the movable member 32 c that functions as an adjuster.

The fixed retaining portion 32 a is fixedly retained to the housing of the sheet ejection device 30 (or to the housing 1A of the image forming apparatus 1). The coupling portion 32 d that receives the one end side of the compression spring 33 is movably disposed to the fixed retaining portion 32 a. Specifically, the coupling portion 32 d is retained to the fixed retaining portion 32 a by a guide mechanism such that the coupling portion 32 d can slidably move in a direction indicated by white arrow in FIG. 2C or in the opposite direction. A detailed description of movement of the coupling portion 32 d is given below.

The rotary retaining portion 32 b is rotatably held to the fixed retaining portion 32 a. Specifically, the rotary retaining portion 32 b is retained to the fixed retaining portion 32 a by a hinge mechanism such that the rotary retaining portion 32 b can rotate in a direction indicated by broken arrow (that is, a counterclockwise direction) in FIG. 2C or in the opposite direction (that is, a clockwise direction).

The movable member 32 c functions as an adjuster to rotate the rotary retaining portion 32 b in the direction indicated by the broken arrow in FIG. 2C and the opposite direction by moving in a given direction. As the movable member 32 c moves, the rotary retaining portion 32 b rotates in the direction indicated by broken arrow in FIG. 2C (or the opposite direction). Then, along with the rotation of the rotary retaining portion 32 b, the sheet stacker 31 rotates in the same direction as the rotary retaining portion 32 b.

It is to be noted that FIG. 2C illustrates a state in which the movable member 32 c, which had been seen at the near side in the direction orthogonal to the drawing sheet of FIG. 2A, has moved to the far side in the direction orthogonal to the drawing sheet and becomes invisible.

As described above, in the present embodiment of this disclosure, the movable member 32 c (that functions as an adjuster) moves (adjusts) to switch the angle of the sheet stacker 31 between a state in which an angle θ1 of (the stacker face of) the sheet stacker 31 is large as illustrated in FIGS. 2A and 2B and a state in which an angle θ2 of (the stacker face of) the sheet stacker 31 is small as illustrated in FIG. 2C.

This switching of the states is performed because the optimum angles θ of the stacker face to stack the sheets P orderly on the sheet stacker 31 are different depending on types of the sheets P stacked on the sheet stacker 31.

To be more specific, the sheets P as plain paper are loaded (stacked) orderly along the inclination of the stacker face, with the stacker face of the sheet stacker 31 having a relatively large angle. Therefore, in a case in which such a sheet P is ejected onto the sheet stacker 31, the angle of the stacker face of the sheet stacker 31 is set to be the angle θ1, as illustrated in FIGS. 2A and 2B.

By contrast, a sheet P such as a thin coated paper has low rigidity and a large frictional resistance on the surface. Therefore, if the stacker face has a large angle, it is difficult for the sheet P to move along the inclination of the stacker face smoothly, and therefore the sheet P is bent and curved. Consequently, the sheets P are not loaded (stacked) orderly on the stacker face of the sheet stacker 31. For this reason, in a case in which such a sheet P is ejected onto the sheet stacker 31, the angle of the stacker face of the sheet stacker 31 is set to be the angle θ2, as illustrated in FIG. 2C.

It is to be noted that, in the present embodiment of this disclosure, the angle θ of the sheet stacker 31 is adjusted from two options. However, the sheet stacker 31 is not limited to the above-described configuration. For example, the angle of the sheet stacker 31 may be adjusted from three or more options or may be adjusted to any required angles.

Here, FIGS. 3A, 3B, and 3C are schematic top views illustrating operations of the retainer 32 of the sheet ejection device 30 and FIGS. 4A and 4B are schematic side views illustrating operations of the sheet ejection device 30′ according to a comparative example. In the present embodiment of this disclosure, rotation of the sheet stacker 31 by the movable member 32 c (that functions as an adjuster) moves the coupling portion 32 d of the retainer 32 that is coupled to the compression spring 33 (that functions as a biasing member).

To be more specific, as the movable member 32 c (an adjuster) rotates the sheet stacker 31, the coupling portion 32 d moves to prevent variation of the biasing force of the compression spring 33. To be more specific, as the movable member 32 c rotates the sheet stacker 31 from the state illustrated in FIG. 2A to the state illustrated in FIG. 2C and the angle θ of the sheet stacker 31 changes from the angle θ1 to the angle θ2, the coupling portion 32 d of the retainer 32 moves in the direction indicted by white arrow in FIG. 2C, along with the rotation of the sheet stacker 31. By contrast, as the movable member 32 c rotates the sheet stacker 31 from the state illustrated in FIG. 2C to the state illustrated in FIG. 2A and the angle θ of the sheet stacker 31 changes from the angle θ2 to the angle θ1, the coupling portion 32 d of the retainer 32 moves in the opposite direction to the direction indicted by white arrow in FIG. 2C, along with the rotation of the sheet stacker 31.

As described above, the coupling portion 32 d of the retainer 32 slides according to the angle θ of the sheet stacker 31. This operation is performed because, as illustrated in FIGS. 4A and 4B, when the angle θ of the sheet stacker 31 varies, the position of the coupling portion 31 d of the sheet stacker 31 also changes. Along with this change, the length of use M of the compression spring 33 significantly changes (i.e., the relation of M1≠M3) and, at the same time, the compression spring 33 is retained not in a straight state but in a twisted state between the coupling portion 31 d and the coupling portion 32 d. Therefore, the compression spring 33 does not bias the sheet stacker 31 in the upward direction normally. If a biasing failure is caused by the compression spring 33 as described above, this failure impairs the function in which the sheet stacker 31 moves in the downward direction along with an increase in the number of sheets P, as explained with reference to FIGS. 2A and 2B. As a result, a stacking failure of the sheet P occurs easily.

By contrast, in the present embodiment of this disclosure, even when the angle θ of the sheet stacker 31 changes, the length of use M1 of the compression spring 33 seldom varies, and the coupling portion 32 d of the retainer 32 slides such that the compression spring 33 is maintained substantially in the straight state between the two coupling portions, which are the coupling portion 31 d of the sheet stacker 31 and the coupling portion 32 d of the retainer 32. Accordingly, the above-described biasing failure occurs less.

Here, in the present embodiment, the coupling portion 32 d of the retainer 32 is configured to move along with movement of the movable member 32 c.

More specifically, when the angle θ of the sheet stacker 31 is the angle θ1 (i.e., in the state illustrated in FIGS. 2A and 2B), the rotary retaining portion 32 b of the retainer 32 is sufficiently separated apart from the fixed retaining portion 32 a of the retainer 32 (i.e., in FIG. 3A). At this time, the movable member 32 c is in contact with a projection of the rotary retaining portion 32 b. This state corresponds to a state in which the rotary retaining portion 32 b is retained at a rotational position illustrated in FIG. 2A. The coupling portion 32 d of the retainer 32 is pushed by the movable member 32 c toward the right side of FIG. 3A, against the biasing force of a spring that biases the retainer 32 toward the left side of FIG. 3A. Consequently, the coupling portion 32 d is located at a position illustrated in FIG. 3A, which corresponds to the position illustrated in FIG. 2A.

Then, as the movable member 32 c is manually moved from the position of FIG. 3A to the position of FIG. 3B, the contact of the movable member 32 c with the projection of the rotary retaining portion 32 b is cancelled (in other words, the movable member 32 c is separated from the projection of the rotary retaining portion 32 b), and the rotary retaining portion 32 b moves to approach the fixed retaining portion 32 a and rotates to the rotational position illustrated in FIG. 2C.

Thereafter, as illustrated in FIG. 3C, when the rotary retaining portion 32 b is brought to contact the fixed retaining portion 32 a, the coupling portion 32 d is released from the pushing by the movable member 32 c to slide to the left side of FIG. 3C due to the biasing force of the above-described spring. It is to be noted that the coupling portion 32 d has a slot 32 d 1 that extends in a longitudinal direction from the lower left side to the upper right side in FIGS. 3A to 3C and that the movable member 32 c has a pin 32 c 1. The pin 32 c 1 of the movable member 32 c is slidably fit into the slot 32 d 1 of the coupling portion 32 d. The coupling portion 32 d moves as the pin 32 c 1 is guided to move along the slot 32 d 1. Consequently, the coupling portion 32 d is operated as described above. Thus, as illustrated in FIG. 2C, the sheet stacker 31 and the rotary retaining portion 32 b rotate to set the angle θ of the stacker face to the angle θ2 and, at the same time, the coupling portion 32 d slides along with the rotation of the sheet stacker 31 and the rotary retaining portion 32 b.

It is to be noted that, when the sheet stacker 31 is rotated from the state illustrated in FIG. 2C to the state illustrated in FIG. 2A, the sheet stacker 31 is rotated manually in the reverse order of the procedure described above with reference to FIGS. 3A to 3C.

Referring to FIG. 2A, the sheet ejection device 30 according to the present embodiment includes guides 34 a and 34 b configured to guide the sheet stacker 31 when the sheet stacker 31 moves in the vertical direction.

To be more specific, in the present embodiment, two sets of the guides 34 a and 34 b are disposed on both sides of the housing of the sheet ejection device 30, in the width direction of the housing of the sheet ejection device 30 (that is, a direction orthogonal to the drawing sheet of FIGS. 2A to 2C), with interposing the sheet stacker 31. In other words, one set of the guides 34 a and 34 b is disposed on one side in the width direction of the housing of the sheet ejection device 30 and the other set of the guides 34 a and 34 b is disposed on the other side in the width direction of the housing of the sheet ejection device 30. The sheet stacker 31 includes shafts 31 a and 31 b, specifically, the shaft 31 a fitting to the guides 34 a and the shaft 31 b fitting to the guides 34 b. The guides 34 a and 34 b extend in the direction orthogonal to the drawing sheet of FIGS. 2A to 2C. With the above-described configuration, the sheet stacker 31 is guided by the guides 34 a and 34 b, within the range of movement of the guides 34 a and 34 b, to move in the vertical direction in a stable state.

Variation.

FIG. 5A is a schematic diagram illustrating a sheet ejection device 30A according to Variation of the embodiment of this disclosure. FIG. 5B is a schematic diagram illustrating the sheet ejection device 30A′ according to the comparative example of FIG. 5A.

As illustrated in FIG. 5A, the sheet ejection device 30A according to Variation includes a stopper 37 that restricts movement of the sheet stacker 31 in the upward direction.

More specifically, the stopper 37 is rotatably supported by the fixed retaining portion 32 a to be rotated manually about a support shaft 37 a. As the stopper 37 is rotated to the position illustrated in FIG. 5A, a tip of the stopper 37 is fit to the shaft 31 a of the sheet stacker 31, so that the shaft 31 a of the sheet stacker 31 does not move up to an upper end of the guide 34 a, due to the biasing force of the compression spring 33. By so doing, the sheet stacker 31 is restricted from moving in the upward direction.

The sheet stacker 31 is restricted from moving in the upward direction because, when the angle θ of the sheet stacker 31 is reduced from the angle θ1 to the angle θ2, as in the sheet ejection device 30A′ illustrated in FIG. 5B, the height from the position of the pair of sheet ejection rollers 25 to the stacker face is changed from the height H1 to the height H2 (<H1), which prevents the sheet P from landing on a target position on the stacker face. Therefore, a stacking failure may occur.

In Variation, the sheet ejection device 30A includes the stopper 37 to adjust an uppermost position of the sheet stacker 31, and therefore, when the angle θ of the sheet stacker 31 is adjusted, occurrence of the above-described stacking failure is reduced.

It is to be noted that, when the angle θ of the sheet stacker 31 is increased from the angle θ2 from the angle θ1 in Variation, the stopper 37 is rotated in order to cancel the above-described restriction of the stopper 37.

As described above, the sheet ejection device 30 according to the present embodiment includes the sheet stacker 31 to stack the sheet(s) P, the retainer 32 to retain the sheet stacker 31 movable in the vertical direction, and the compression spring 33 (that functions as a biasing member) that is coupled to the sheet stacker 31 and the retainer 32 and biases the sheet stacker 31 in the upward direction. The sheet stacker 31 moves in the downward direction against the biasing force of the compression spring 33 as the number of sheets P stacked on the stacker face increases. The retainer 32 includes the movable member 32 c (that functions as an adjuster) to rotate the sheet stacker 31 so as to adjust the angle θ of the sheet stacker 31. Consequently, as the movable member 32 c rotates the sheet stacker 31, the coupling portion 32 d of the retainer 32 to which the compression spring 33 is coupled moves.

According to this configuration, regardless of the number or types of the sheets P stacked on the sheet stacker 31, the sheets P are stacked orderly on the sheet stacker 31.

It is to be noted that the present embodiment of this disclosure is applied to the sheet ejection device 30 provided to the image forming apparatus 1 that performs monochrome image formation. However, this disclosure is not limited to the above-described sheet ejection device (that is, the sheet ejection device 30). For example, this disclosure is also applicable to a sheet ejection device provided to an image forming apparatus that performs color image formation.

Further, it is to be noted that the present embodiment of this disclosure is applied to the sheet ejection device 30 provided to the image forming apparatus 1 that employs electrophotography. However, this disclosure is not limited to the above-described sheet ejection device (that is, the sheet ejection device 30 and the sheet ejection device 30A). For example, this disclosure is also applicable to a sheet ejection device provided to an image forming apparatus that employs, for example, an inkjet method or a stencil printing machine.

Furthermore, it is to be noted that the present embodiment of this disclosure is applied to the sheet ejection device 30, which is provided to the image forming apparatus 1, or to the sheet ejection device 30A of Variation, for ejecting the sheet P after image formation. However, this disclosure is not limited to the above-described sheet ejection device (that is, the sheet ejection device 30 or the sheet ejection device 30A). For example, this disclosure is also applicable to the document conveying unit 10 (i.e., the automatic document feeder (ADF)) as a sheet ejection device to which the original document D, which functions as a sheet, is ejected.

Further, even when the above-described sheet ejection devices are applied, these sheet ejection devices can achieve the same effect as the effect provided by the configuration(s) in the present embodiment.

It is to be noted that the above-described embodiments are illustrative and do not limit this disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements at least one of features of different illustrative and exemplary embodiments herein may be combined with each other at least one of substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the above-described embodiments and thus may be preferably set.

It is to be noted that a “sheet” in the above-described embodiments of this disclosure is not limited to indicate a (regular) paper but also includes any other sheet-like recording medium such as coated paper, label paper, overhead projector (OHP) sheet, metal sheet, film, prepreg, cloth, and the like.

The effects described in the embodiments of this disclosure are listed as most preferable effects derived from this disclosure, and therefore are not intended to limit to the embodiments of this disclosure.

The embodiments described above are presented as an example to implement this disclosure. The embodiments described above are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, or changes can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of this disclosure, and are included in the scope of the invention recited in the claims and its equivalent.

Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above. 

What is claimed is:
 1. A sheet ejection device comprising: a sheet stacker having a stacker face and a coupling portion, the sheet stacker configured to stack a sheet on the stacker face; a retainer having a coupling portion and an adjuster configured to rotate the sheet stacker to adjust an angle of the stacker face, the retainer configured to retain the sheet stacker to be movable in a vertical direction; and a biasing member coupled to the sheet stacker and the retainer and configured to apply a biasing force to bias the sheet stacker in an upward direction to the retainer, the sheet stacker being configured to move in a downward direction against the biasing force of the biasing member, as a number of sheets stacked on the stacker face of the sheet stacker increases, the coupling portion of the retainer, to which the biasing member is coupled, being configured to move when the adjuster of the retainer rotates the sheet stacker.
 2. The sheet ejection device according to claim 1, wherein the coupling portion of the retainer moves to prevent the biasing force of the biasing member from varying when the adjuster rotates the sheet stacker.
 3. The sheet ejection device according to claim 1, wherein the retainer includes: a fixed retaining portion on which the coupling portion of the retainer is movably disposed; a rotary retaining portion rotatably held relative to the fixed retaining portion; and a movable member that is the adjuster configured to move in a given direction to rotate the rotary retaining portion; and wherein the coupling portion of the retainer is configured to move along with movement of the movable member.
 4. The sheet ejection device according to claim 1, further comprising: a guide configured to guide the sheet stacker in movement in the vertical direction.
 5. The sheet ejection device according to claim 1, further comprising: a stopper configured to restrict movement of the sheet stacker in the upward direction.
 6. The sheet ejection device according to claim 1, wherein the adjuster is configured to be operated manually.
 7. The sheet ejection device according to claim 1, wherein the biasing member is a compression spring.
 8. An image forming apparatus comprising: an image forming device configured form an image on a sheet; a sheet ejection unit configured to eject the sheet on which the image is formed by the image forming device; and the sheet ejection device according to claim 1, configured to stack the sheet ejected by the sheet ejection unit. 